This invention broadly belongs to the field of continuous or semi-continuous material web processing such as textile material or paper web processing in order to impart improved properties thereto. In its more specific aspects, the present invention comprises a new and useful apparatus and method to apply controlled amounts of treating liquor to a liquid receptive material web such as textile or paper webs. The apparatus of this invention has been designed and developped especially, but not exclusively, to improve the performing of the so-called M.A. process (i.e. minimum application process) basically disclosed in U.S. Pat. No. 3,811 834. The present invention further relates to new and useful liquors especially adapted to the method of this invention.
The M.A. process and the machines used for its realisation allow to perform a continuous application of relatively concentrated solutions, emulsions and dispersions of finishing or treatment agents which are evenly to be distributed in porous webs such as textile and paper, under rather high material speeds. In this process, the amounts of treating liquor used do no longer exceed the amounts strictly necessary to achieve the desired effects as it has been currently the case before, e.g. on the pad mangle. The M.A. process permits, compared with earlier technics such as the pad mangle, substantial energy savings or a highly improved effectiveness of the drier devices. Furthermore, cellulose crosslinking reagents surprisingly give an improved yield in that the same amounts of agents as used before, expressed as 100% active finishing agent per unit of area, yield better finishing effects; should these effects be quantitatively the same, a better abrasion resistance is achieved and the amounts of active agents are reduced by at least 10%.
The M.A. process distinguishes over the spraying and foam application processes promoted in the very last time as being particularly simple, also regarding the machines to be used, and in that a very uniform application and high working speed can be achieved. Foam application methods show serious technological problems regarding foam stability, foam composition and the control of the amount to be applied.
The M.A. process and the machines to be used are disclosed and explained in detail in above mentioned U.S. Pat. No. 3,811,834, in Swiss Pat. Nos. 530,233 and 533,074 and in Textilveredlung 10,1975, p.15-20.
The M.A. process is particularly suited for the continuous and homogeneous finishing of cellulosic textile webs, i.e. such which are composed exclusively or in the major part of cellulose fibers, by means of reactive finishing agents. The process has first of all been designed and developed for the application of curing resins with subsequent condensation on substantially dry textile webs. Of course, any other liquor or bath which contain substances capable of curing or of reacting with cellulose, may be applied continuously and evenly in the described manner
During the use of the process for many years and the construction of the machines which can be used in the process, it has been found necessary to develop further this technical solution, in particular for special problems.
The M.A. machines allow the processing of smooth textile webs. However, should the starting textile material contain crumples and creases and still other wrinkles, e.g. staple wrinkles, the liquor application is slightly uneven. This unevenness normally does not create any problem in high performance finishing since they are invisible and affect only small portions. However, things change should the liquor contain visible components like optical brighteners or dyestuffs. The visible image is than impaired, and this negative aspect is enhanced by the unevenness of any high performance finishing which may be applied simultaneously.
One of the major objects of this invention is to solve this problem; the apparatus to be designed should be constructed such that any desired treating liquor application, be it a minimum application or not, can be effected on any liquid receptive web whatsoever in a continuous, controlled and even manner, and that unevennesses of the web do not result in corresponding unevenneeses in the liquor application. Such unevennesses are wrinkles, knots, sewings, pillings and so on.
Furthermore, it has been observed with the M.A. process that a starting textile web, particularly very lightweight fabrics, begin to flutter at very high process speeds, such resulting in unevennesses of the liquor application. It must however be noted that such speeds had originally never been contemplated and are situated well above 100 m/min. It is a further object of this invention to resolve this problem of fluttering too.
A further difficulty on a certain application of the M.A. process is encountered with knitted fabrics. Since the textile web is drawn in the M.A. process through the treating machine (this is the case with nearly all textile machines) and must be guided sliding over an application roll, the textile web generally travelling faster than the roll surface, a certain resistance in the form of a drawing tension is accumulated in the textile web, that tension being of the order of about 200 N when the web is 2 m wide. This tension will result on a knitted fabric in a curling of the web edges; the web being normally a lengthwise opened tube. But also flat knitted fabrics behave in the same manner. If the pulling tension is increased, the edges of the web show still more curling. There is a further object of this invention that knitted fabrics could be passed over the applicator roll in a flat and smooth state and only on the very low lengthwise and transverse tension. Models and suggestions to resolve these problems do not exist since furthermore it has been found, and this renders the problem still more serious, that knitted fabrics absorbe much more liquor than a woven fabric having a comparable rate per unit area.
The objects of the instant invention could only be approached and met by a combination of different means and measures which had to be found one after another independently from each other
First, it should be noted that a kind of pad mangle as an applicator could not be contemplated since the pad mangle has only very limited control possibilities. A variation of the applicated amount can in practice only be obtained by means of the liquor concentration, and this is complicated and material and energy wasting.
The first approach to the objects of the invention was the introduction of a supported material condition. This condition can be defined with reference to FIG. 1: a steel roll 6, discharged by a counterweight 9 or by spring means (not shown), is arranged some degrees of an angle (angle .beta.) in front of the normal contact line of a textile web 4 with an applicator ro1l 1, see the schematic illustration of FIG. 1. The applicator roll 1 rotates in the liquor 2 containing vat 3 and is coated with a hydrophilic rubber coating 1a indicated in dashed lines, this rubber being used to enhance the forming of a uniform liquor film on the surface of the applicator roIl which will remain uniform until its absorption by the textile material. The textile web 4 is drawn around a deflection roll 5 and then over the applicator roll 1. The steel guide roll 6 which is journalled in an arm 7 pivotable around point 8, is resting with little force on the textile web 4. The counterweight 9 and its lever arm are so selected that the relief of the guide roll 6 is optimised. The contact line of the guide roll 6 with the applicator roll 1--these two rolls have parallel axes--is selected as to be situated by an angle .beta. of few degrees in front of the normal contact line 10 which would be the real contact line of the web 4' with the applicator roll 1 should the guide roll 6 not exist.
The expression "supported web condition" has been taken from the technic of mercerising where it is often used. It will express the fact that the web is not free travelling but supported on one side when it is transmitted to another machine element such as another roller.
This expression, however, does not mean that the material is opened to the arriving liquor since the tangential introduction of the web into the nip of two rolls does not open the web and is nevertheless a supported web condition.
The expression "applicator roll" means that this roll which is, in the contrary to the so called padding roll, not coupled with the material web sliding over it and to be supplied with liquor in the sense of the same speed of the travelling web and the roll surface. This will say that the applicator roll has generally a surface speed which is generally independent on the web speed and can be adjusted. The applicator roll may serve as the regulating element in a regulating or control circuit.
The installation described above could however not resolve the problems discussed above in a satisfactory manner, especially with regard to high processing speeds and the treatment of knitted fabrics. The partially balanced counter-roll causes occasional lift-off of the textile web on the entire width of the applicator roll so that the described solution could not be retained. However, this solution was successful for wrinkle containing textile webs where a uniform application of finishing liquors could be achieved and which was nearly impossible to obtain without the guide roll.
Then, it has been tried to mount the counter-roll with a fixed nip, considering that it should be possible to equalize wrinkels in the nip between applicator roll and counter-roll and to optimise spread-out of the textile web.
Corresponding experiments were however not successful since on one hand, a fixed counter-roll of steel amplifies in an unacceptable degree the frictional retarding effect on the material web which also must slide over the rubber surface of the applicator roll so that the drawing tensions in the material web became too high. On the other hand, the relatively hard rubber applicator roll is not fitted to absorb sewings in the supplied textile web which represent twice the material thickness.
Finally, the rubber applicator roll is easily damaged mechanically so that the liquor film is no longer uniform. The cleaning of the rubber applicator roll is particularly difficult due to its microporosity.
Now, in order to implement the objects of the invention mentioned above and still further other objects which will become more readily apparent as the description proceeds, it has been found that an applicator roll having a metallic surface, preferably with a certain defined surface quality, and a counter-roll having a resilient but skid resistant surface which is mounted in a constant but adjustable distance to the applicator roll and being parallel thereto, is used, that surface being capable to absorb uneven portions of said web. This combination of features is surprising since the wettability of metals by the aqueous liquors of the material finishing or treatment is generally insatisfactory.
Basically, it is not too difficult to produce a continuous and uniform water film on a metal surface; this is for example achieved by the cleaning of the matal and the addition of a tenside to the water. However, in the present case, the treating liquors are given ones and contain normally components which counteract to the forming of the film but which cannot be foregone. Furthermore, the liquor composition can only be modified with a great precaution since the liquor is optimised in view of the desired finishing effects. The free addition of high efficient tensides particularly impossible since these tensides, although they improve the forming of the film, act generally as strong foam formers and would therefore render impossible the production of thin, uniform and bubble free films on the applicator roll.
A further object of the present invention is now implemented by a new class of treatment liquors in that a special film forming test has been developed to screen liquors which are capable of forming a continuous and uniform film on a metal surface. The aqueous liquors typically contain special tensides; they are characterized by the fact that they fulfill the film forming test to be described later. The invention is seen in the combination of certain properties of the liquor with the use of an applicator roll having a metal surface; treating liquors known per se may be used as far as they fulfill film forming test.
The applicator roll consists at least on its surface of such a metal which requires a very smooth surface structure in the process by the polishing action of the material web. A preferred material is stainless steel; for example the roll surface has been smoothed to a roughness grade N5 according to VSM 10230/31.
The counter-roll must be arranged thus that the material web first contacts the liquor film in the roll nip or shortly before, i.e. that the web is opened to the liquor and is simultaneously in supported condition, i.e. it is supported from behind by the counter-roll.
It has now surprisingly be found that the nip of the counter-roll and the applicator roll can be adjusted to a thickness which is less than the mean thickness of the material web. This is probably due to the resilience, normally the rubber elasticity, of the counter-roll. It could not have been foreseen that the material web would not acquire unacceptable tensions and distorsions under these conditions, its speed being typically higher than that of the applicator roll. Even a destruction of the web would have to be considered.
In fact, the thickness of the nips can be adjusted in the limits defined below, and the retaining force in the material web can be adjusted.
The thickness of the roll nip is less than the mean thickness of the material web. This will say that the counter-roll is slightly flattened in the nip, at least if the web is not sufficiently compressible. The thickness of the roll nip is preferable 60 to 80% of the mean thickness of the material web. This mean thickness is measured according to SNV 98411 (this corresponds to DIN 53855 and ASTM D 1777-64). The counter-roll has a resilient surface. Preferably, this surface comprises a thick coating of nitrile rubber having a Shore hardness of about 35. Still softer qualities can be used.
The counter-roll may also be a brush roll having very closely set brushes, a sponge rubber or plastic sponge roll, a felt roll, a velvet roll, a step roll, a suction roll etc. It is important that the surface is non-skidding for the material web.
The adjustment of the fixed distance of the counter-roll to the applicator roll can be made by hand or by electro-mechanical, hydraulic or pneumatic means. It is preferred to display simultaneously the value of the nip thickness. Since the thickness of the material web may vary when the material web proceeds, an automatic adjustment of the roll nip is appropriate. This can easily be managed since the weight per unit area of the web is particularly measured before the application of treatment liquor; the corresponding measuring device is generally combined with a thickness measuring apparatus, or one might calculate the function of the thickness dependent upon the rate per unit area, and this function is used. And said value for the thickness of the roll-nip is then introduced (for example 75% of the average material web thickness) which will then be kept constant by control devices known per se.
At least two doctor blades are preferably attached to the applicator roll. The first blade is situated at the surface region between the take-off line of the web and the dipping line of the roll into the liquor and serves to remove dirt, particles and film residues optionally present. The removed material is discarded or recycled after cleaning processing. The second doctor blade is arranged below the liquor level in the liquor vat and serves to remove residual film bubbles and for controlling the current of the liquor around the applicator roll surface.
Since the counter-roll it has no resilient support, a guide-roller 5 which had first been provided, see FIG. 1 is no longer necessary. The counter-roll can be free running or may be driven. When a thin and light material web or knitted fabrics are processed or high travelling speeds are used, the counter-roll should be positively driven.
Without being bound by any theory, the inventors suppose that the following phases are encountered on carrying out the process, and these phases are schematically illustrated in FIG. 3a to 3c:
1. Phase I (FIG. 3a)
The porous web 4 passes over the rubber counter-roll 6, is transformed into the convex configuration and opened to the liquor film F coming from the application roll 1. In the moment of the contact, the liquor film F can better enter into the open hollow spaces H of the web. Due to the high speeds and the speed difference between applicator roll and material web already mentioned, the film is distributed into droplets, and the absorption of the liquor is enhanced.
2. Phase II (FIG. 3b)
The liquor containing web 4 is compressed in the nip of the rolls 1 and 6 under elastic deformation of the counter-roll 6 as well as of the web 4. The preceding material opening is abolished, and the web is transformed into a weakly concave configuration. This fulfill all mechanical and physical conditions for an even distribution of the liquor in the material web. The absorbed liquor is brought in close contact with the material structure by the pression on the material. Furthermore, the web is slightly opened to its backside thus creating a suction effect on the liquor.
These actions are favoured by the use of substantially foam free liquors which do not introduce an air pad into the material web.
3. Phase III (FIG. 3c)
In this third phase wherein the web 4 is still in contact with the applicator roll, the take-up and the distribution of the liquor are completed as far as necessary since the compression of the web has been cancelled. This further contact can be expressed as an angle at centre (e.g. .alpha..sub.1, FIG. 2) of the application roll, as a length (distance on periphery, or as a dwell time. A dwell time expression is preferred since the distribution of the liquor is a function of time. The contact angle is selected to about 2.degree. to 15.degree. corresponding to a length of about 6 to 40 cm on the roll surface and a dwell time of about 0.02 to 0.2 sec. When low material speeds are used, the liquor has sufficient time to pass completely from the applicator 1 into the web 4, and the web can directly be taken-off from the applicator roll in (arrow I in FIG. 3c). The value of the contact angle may be used to further control the retaining force in the web.
The take up of the liquor by the material web depends upon the proportion of the affinity of the liquor to the material web 4 and to the surface of the applicator roll 1. The normally remaining film boundary layer of the liquor is reduced when the web travels faster than the surface of the applicator roll 1, and this case is preferred in this invention. Due to this relative mouvement between web and the applicator, the latter is continuously cleaned and smoothened.
A special problem is the application of treating liquor to knitted fabrics in the M.A. process. It is known that problems exist in passing this textile product through treatment machines due to its special open structure. A drawing tension in lengthwise direction leads to a shrinking of the web in transverse direction. The web edges have a very strong tendency to curl, and curling angles of more than 360.degree. can be observed particularly on opened knitted tubes.
This invention renders possible the treatment in the described apparatus even on high process speeds when the web of knitted fabrics is struck even on the counter-roll by a gaseous flow, especially airflow, coming from appropriately shaped air nozzles. The material web is preferably first passed over a lath roller for centering and spreadening of the web, especially before reaching the first weight measuring device; between this device and the counter-roll, the web passes a novel flat air spreadening apparatus. Other preferred devices will be described later.
The use of a metal applicator roll, for example of steel, which has been developed in this invention opens new and useful possibilities to improve the process. Such rolls are typically constructed as hollow rolls to save weight, and the use of a hollow shaft allows to thermostate the roll by passing a corresponding heated or cooled flow medium, thus allowing to exactly control the film quality, the liquor concentration and other liquor properties including evaporation speed. This has not yet been possible with the applicator roll used until now which has a thick rubber surface layer and therefore bad thermic properties. Only the use of a metal roll having a very smooth and pore free surface as an applicator roll by this invention allows for the first time a compression of the material web since the surface friction of the web is still acceptable at the preferred speed differences between web and roll surface. Finally, such a roll can easily been cleaned and kept clean.
The invention further concerns a process for applying of a treating agent to a liquid receptive material web and furthermore a treating bath.
The process of this invention is not limited to the application of reactive finishing agents to cellulose containing textile materials. It can also be used to apply any liquor whatsoever, also non-aqueous ones, of any composition to any liquid receptive and flexible web materials whatsoever, and this application can be used to achieve a homogenous distribution or a one-side treatment. The material of the web needs not to be hydrophilic but must be liquid receptive. The liquors need only fulfill the film test described below and should generally pass the foam forming test also defined below.
Liquid receptive and flexible materials in web form are firstly textile webs, namely fabrics, knitted fabrics and non-wovens of known textile fibres, for example native and regenerated cellulose, wool, man-made fibres like polyester, polyolefine, polyacryl, polyvinylchloride, polyamide, glass, asbestos and other mineral fibres like stone and slag wool. Furthermore, natural and synthetic paper and thin cardboard can be used. Sheets formed by a plurality of parallel yarns, for example warp yarns, which are in mutual lateral contact and may also form two and more layers, can also be treated. The material may also be damp but not so wet that the liquor is squeezed out in the roll nip.
The application of the liquor leads generally to a homogeneous distribution thereof within the web material. Under normal conditions for which the M.A. process has originally been developed, a liquor applied to one side of the web forms therein a liquor distribution which is even throughout the substrate. However, the present invention is not limited to this effect.
Further, very interesting possibility for the use of the new apparatus is the wet-in-wet technic or the controlled addition application. This method allows to save one drying step. It uses as a starting material a web which still is damp, for example a web coming after the dyeing step from a pad mangle, and this web is impregnated in the apparatus of the invention with minor but controlled amounts of another liquor. It is possible to apply a pre-determinated, constant amount of liquor, e.g. 10 g/m2 or 20 g/m2 or, alternatively, the "missing" until predeterminated value of total liquor, namely dyeing liquor plus second 1iquor, is completed.
This method may usefully be applied for dyeings, for example reactive dyeings, where the dyestuffs and the fixation agents are applied successively or where different dyeing liquors are successively to be supplied. But also for other combinations, for instance dyeing and hydrophobic finishing, this addition application may advantageously be used.
Sometimes a migration of applied substances in the web material is desired, e.g. dispersion dyes in polyester fabrics. In these cases, such amounts of liquor are applied by means of the apparatus of the invention that during subsequent drying, the optimum value of migration will be obtained and as s result one obtains fabrics which are particularly level dyed in very unexpensive manner. This method is termed by the applicants as a "controlled addition application".
Substantial advantages of the new apparatus and of the process, particularly in contrast to pad mangles and pad mangling, are first a better control possibility of the applicated liquor--such a control is virtually absent in pad mangles--, the constance of the applicated amounts in transverse direction of the web due to the absence of sagging rolls and the absence of variations in the liquor.
In some cases it will be desirable to modify the described technics, processes and methods and to wish to have an uneven application, for exemple should the web material undergo a crepe formation or an effect dyeing. This effect can be achieved according to this invention by disturbing the film conducted by the applicator roller. The distortion of the film should be a random one, i.e. without noticeable uniformity. This can be performed by means of a toothed doctor blade which is moved horizontally to and fro on the liquor film of the applicator roll with a randomly changing speed or driven by corresponding pulses, by means of an irregular blowing on the film and so on.